Some medical treatment devices are based on applying electrical stimulation signals to target neural tissue. Typically a peripheral nerve receives the electrical stimulation from an implantable electrode that is inserted into nearby host tissue. It is important that such an implantable electrode be securely fixed at its implantation site to avoid post-surgical migration, which can reduce the electrode's ability to adequately stimulate the nerve.
Existing implantable electrodes, such as the pacing electrodes made by Medtronic, Boston Scientific, St. Jude, Biotronik USA and Osypka, use either active fixation mechanisms such as a helical screw fixation tips, or passive fixation mechanisms such silicone/polyurethane tines along the length of the electrode lead or at the distal tip. For example, U.S. Patent Publication 20120323253 by Garai describes an implantable electrode array with an active anchor tip that initially is retracted within the electrode lead. Then during implantation surgery, the anchor tip can be extended outside the rest of the lead for tissue fixation.
U.S. Pat. No. 5,693,081 by Fain describes an implantable electrode with a hook fixation element that is both active and passive. The fixation hook is located approximately back from the distal tip of the lead and is adapted to move out away from the electrode body to stick out at an angle of 90 degrees and then be rotated with the lead to hook into the adjacent tissue. The Fain arrangement is quite complicated and given the diameter of an actual electrode lead may not be feasible.